The Saturdays star, who is expecting her first child with Wayne Bridge, filled in for Rochelle on last night's (4 June) episode of Sweat The Small Stuff on BBC Three, as Rochelle is currently playing doting mum to her two-week daughter Alaia-Mai.
When host Nick Grimshaw asked if Frankie (who filmed the spot before she swapped her cropped hair for long extensions) had met Alaia-Mai yet, she replied: "She is gorgeous. She is tiny!"
And when asked how it made her feel about her own pregnancy, the 24-year-old joked: "More fearful! I was like, 'Okay, so there is actually a baby at the end of this. Wayne! We need to prepare for this!'
Nick also pointed out that Frankie and Wayne's baby was bound to be a beauty thanks to their combined good looks, but Frankie wasn't too sure…
"Sometimes you have good genes and it can go terribly wrong, can't it?" she joked.
Nick then asked what she'd do if she has an "ugly" baby (oh, Nick, there is no such thing as an ugly baby), prompting Frankie to laugh: "I'd put it back in until it's finished!"
Frankie announced her happy baby news in May, a month after revealing that she was engaged to her footballer boyfriend.
The star showed off her growing baby bump on the red carpet at last night's glitzy Glamour Women of the Year Awards in London, which she attended with band mates Mollie King, Una Healy and Vanessa White.
> Frankie Sandford's new hair extensions: before and after pictures!
> Rochelle and Marvin Humes enjoy first night out since baby's birth: photo!
Frankie isn't the only pregnant star. Check out who else is expecting in our gallery!